Fix Photoshop Scratch Disk Full Error

Symptoms

When working in Adobe Photoshop, you may encounter an error message stating that the scratch disk is full. This often occurs during intensive tasks such as editing large files, applying filters, or running history states. Symptoms include inability to save, perform undo operations, or apply certain effects. The application may freeze or crash.

Root Causes

The scratch disk is a designated drive or partition that Photoshop uses as virtual memory when RAM is insufficient. The error arises when this disk runs out of free space. Common causes include:

• Insufficient free space on the primary scratch disk (often the boot drive).
• Multiple large temporary files accumulated by Photoshop.
• Incorrect scratch disk configuration (e.g., using a slow or nearly full drive).
• Running out of RAM causing heavy reliance on scratch disk.
• Other applications consuming disk space.

Step-by-Step Fix

Step 1: Free Up Space on Current Scratch Disk

1. Close Photoshop and all other applications.
2. Open File Explorer (Windows) or Finder (Mac).
3. Navigate to the drive currently set as scratch disk (default is boot drive).
4. Delete unnecessary files: empty Recycle Bin/Trash, remove temporary downloads, uninstall unused programs.
5. Run Disk Cleanup (Windows): Right-click drive > Properties > Disk Cleanup. On Mac, use Storage Management.
6. Ensure at least 20-50 GB of free space for large projects.

Step 2: Change Scratch Disk Assignment

1. Launch Photoshop. Immediately hold Ctrl+Alt (Windows) or Cmd+Option (Mac) to open Scratch Disk Preferences before the application fully loads.
2. Alternatively, go to Edit > Preferences > Scratch Disks (Windows) or Photoshop > Preferences > Scratch Disks (Mac).
3. Uncheck the current full drive. Check one or more drives with ample free space (preferably an internal SSD).
4. Reorder the list: fastest drive first (SSD > HDD). Use arrow buttons.
5. Click OK and restart Photoshop.

Step 3: Clear Photoshop Temporary Files

1. Close Photoshop.
2. Navigate to the temporary folder: C:\Users\[username]\AppData\Local\Temp (Windows) or /private/var/tmp (Mac).
3. Delete any files starting with ~PST or Photoshop Temp.
4. Also clear the scratch disk folder: C:\Users\[username]\AppData\Roaming\Adobe\Adobe Photoshop [version]\Adobe Photoshop [version] Settings\ and delete large temp files.
5. Empty Recycle Bin/Trash.

Step 4: Optimize Photoshop Performance Settings

1. Go to Edit > Preferences > Performance.
2. Increase RAM usage for Photoshop (recommended 70-80% of available RAM).
3. Set History States to a lower number (e.g., 20-30).
4. Enable Use Graphics Processor if available.
5. Set Cache Levels to 4-6 for normal use.
6. Click OK and restart.

Alternative Fixes

• Use an External SSD: Connect a fast external SSD and set it as primary scratch disk.
• Increase Virtual Memory: On Windows, increase page file size. On Mac, ensure swap is on a fast drive.
• Reduce File Size: Flatten layers, merge visible, or save as smaller format (JPEG) to reduce scratch disk usage.
• Reset Photoshop Preferences: Hold Ctrl+Alt+Shift (Windows) or Cmd+Option+Shift (Mac) while launching Photoshop. Confirm reset.

Prevention

• Regularly monitor free disk space on scratch drives. Keep at least 20% free.
• Use a dedicated fast SSD (internal or external) solely for scratch disk.
• Close unnecessary applications to free RAM.
• Periodically clear Photoshop temp files and cache.
• Update Photoshop to the latest version for performance improvements.
• Consider upgrading RAM if you frequently work with large files.

By following these steps, you can resolve the scratch disk full error and maintain smooth Photoshop performance.